The present invention relates to a motor-driven photographic camera in general, and more particularly to a photographic camera capable of recording a series of individual images at predetermined time intervals in the photosensitive material of consecutive sections of a photographic record carrier strip.
There are already known various constructions of photographic cameras of this type. In one such conventional construction, there is provided a camera body which essentially consists of a front plate equipped with an objective-mounting arrangement, and of a frame or support constructed to accommodate and/or support a common drive operative for simultaneously driving a rotatable shutter which is arranged at the front plate and moves in front of an exposure opening to periodically obscure and expose the same, and an arrangement for transporting a film strip, which is accommodated in a cassette that is arranged rearwardly of the front plate on the support, on an intermittent basis past the exposure opening and behind the same. In this construction, the common drive essentially includes an electric motor with a worm gear for driving the shutter in rotation, and a transmission from the electric motor to a frictional stepping drive for incrementallyadvancing the film strip past the exposure opening, the frictional stepping drive including a friction segment cylinder driven in rotation and intermittently engaging one of the major surfaces of the film strip and a friction counterroller which is mounted for free rotation across the film strip from the friction segment cylinder and engages the other major surface of the film strip opposite to the region of engagement of the friction segment cylinder with the one major surface of the film strip. Furthermore, this conventionally constructed camera includes an entraining shaft or capstan for the takeup spool or core for the film strip, the entraining shaft being also intermittently driven in rotation in dependence on the friction segment cylinder. Such an arrangement is suited for the automatic taking of a series of photographic pictures.
Cameras of this construction, which are equipped with stepping image-recordation control or, in other words, with a stepping advancement of the film strip for the automatic recordation of a series of individual images in the photosensitive material of consecutive sections of the film strip, can be used in various fields of human endeavor and they are particularly suited to record, in a documentary fashion, the development of a situation or activity in a substantial number of individual photographic images or snapshots which have a very high degree of sharpness and precision considering the circumstances, such as the available light. One of the main areas for use of cameras of this type is in establishments which are freely accessible to and frequented by the public, such as the areas in front of the teller windows in bank or saving institution branch offices, to secure documentary evidence in the event of criminal hold-ups and muggings. Another one of the numerous possible applications of such cameras is in the traffic supervision and/or control on the public roadways of throughfares.
The commercially available photographic cameras which are equipped with the stepping image-recordation control or film advancement mechanisms can be used for these and similar purposes only to a limited extent, if for no other reason, then because of their limited film-storage capacity. For this reason, there have been developed specialized photographic cameras for use in these applications. However, experience with the conventional cameras which have been specially developed for this purpose has shown that they still leave much to be desired in many respects and that they do not satisfy all the requirements to be satisfied by such cameras.
One conventional camera construction which has been specially developed for the above-mentioned applications is known from the German Pat. No. 28 32 539, wherein the shutter disc, which is constructed as a rotary segment disc, is driven in rotation, and the film strip is intermittently or incrementally advanced by a friction stepping mechanism, in dependence on the rotation of the output shaft of an electric motor. However, the measures, which are taken in this conventional arrangement in order to assure exact synchronization of the rotational movement of the shutter disc in front of the exposure opening of the camera with the incremental advancement of the film strip by means of the friction stepping mechanism during the advancing phases of operation which coincide with the phase of operation of the shutter disc in which the latter obscures the exposure opening of the camera, are relatively expensive and require a substantial amount of available space. Thus, in this conventional camera, the electric motor is arranged at the underside of a support part of the camera body, which extends rearwardly from a front plate of the camera body, the driving shaft for the shutter disc also extends along the underside of the support part of the camera body, and only this driving shaft is directly driven by the electric motor by means of a worm gear transmission, while a further gear transmission, this time a bevel gear transmission, is arranged on and at the driving shaft for the shutter disc, and a toothed-belt transmission is provided for driving the stepping friction mechanism for the film advancement, in order to assure that the friction segment cylinder or roller of the stepping friction mechanism is positively driven in rotation in synchronism with the angular displacement of the shutter disc. In addition thereto, the shaft or capstan for the takeup reel or core for the film strip is caused to rotate by another transmission which includes a friction wheel or roller which engages the outer surface of the toothed belt. As advantageous as this known arrangement may be in certain respects, it is also possessed of several important drawbacks. So, for instance, it is very difficult in this known arrangement to adjust the intermittent advancement of the film strip in such a relation to the angular displacement of the shutter disc about its axis of rotation that the advancing phase of the operation of the stepping friction mechanism accurately coincides with the covering phase of operation of the shutter disc during which the shutter disc covers the exposure opening provided in the front plate of the body of the camera, that is, during which the sector-shaped slit of the shutter disc is out of registry with the exposure opening. Another disadvantage of this arrangement is that the friction transmission for driving the entraining shaft or capstan for the takeup reel or core for the film strip, which includes the friction roller engaging the outer surface of the toothed belt, can be accommodated only within relatively narrow limits to the angular velocity of the takeup core which decreases with the increasing diameter of the film material wound around this core; in addition thereto, as the diameter of the body of film material wound around the takeup core increases, the torque required for rotating this core increases as well at a rapid pace which, in certain circumstances, could result in slippage between the friction roller and the outer surface of the toothed belt.